ON THE EVIDENCE FOR TEMPERATURE SEICHES. 
EDWARD A. BIRGE. 
[Notes from the Laboratory of the Wisconsin Geological and Natural History 
Survey. VI.] 
The term temperature seiche was introduced by Watson (’04) 
in discussing certain periodic oscillations of temperature in 
the deep water of Loch Ness. He thought that these oscilla¬ 
tions show that the isotherms of the lower water “are swinging 
as a whole about a transverse central axis. 7 ’ His explanation 
conceived a swinging of the hypolimnion*, as if the thermo- 
oline were the upper surface of water in a trough, above which 
floated a layer of lighter oil, representing the epilimnion. 
In 1907 Wedderburn ( 7 07 a) reported experiments on a trough 
thus arranged, showing the possibility of a seiche, such as that 
postulated by Watson. Watson computed the period of a 
seiche in the hypolimnion of Loch Ness and found that it agreed 
with the observed period of the oscillations of temperature. 
His paper reported only the temperatures found at the depth 
of 200 feet, where the maximum oscillations occurred, and no 
profitable criticism of his theory could be made until the whole 
series of temperature records was published. This was done 
* I employ two new words in this paper, which seem convenient in 
writing of the temperature and other phenomena of lakes. These terms 
are epilimnion, for the upper warm layer of water which develops in the 
lake in summer, and hypolimnion, for the lower colder water. These 
two parts of the lake differ widely in their temperature changes, as well 
as in their chemical and biological phenomena. It seems advisable, 
therefore, to assign definite names to them. The word thermocline, first 
used by me in 1897, is the equivalent of Richter’s term Sprungschicht, 
or the discontinuity layer of Wedderburn. It lies at the top of the hypo¬ 
limnion. 
2—S. & A.—3 
